A&P - Week 3: Metabolism, Plasma Membrane

The sum of all biochemical reactions inside a living cell, involving nutrients

Make things. They transfer energy from ATP to complex molecules

Break things down. They transfer energy from complex molecules to ATP

Metabolism

Via the blood

(a) build complex molecules (b) form pyruvic acid and acetyl Coenzyme A (CoA)

In the mitochondria. These reactions are almost entirely catabolic

Oxygen is used to break down food into carbon dioxide and water, producing ATP. These byproducts (CO2 and H2O) are exhaled.

Glucose

Involve the gain of oxygen or loss of hydrogen atoms (and their electrons). Oxidized substances: lose electrons and energy. Reduced substances: gain electrons and energy.

Glucose has many hydrogen atoms. It could release energy by highly oxidizing it with many oxygen atoms or double-bonds.

• C6H12O6 (glucose) is oxidized to CO2 (carbon dioxide)

• O2 (oxygen) is reduced to water (H2O)

• Released energy is used to make ATP

They occur under very controlled conditions, preferably one reaction at a time. This is so that there isn't too much energy at once, potentially causing a hazard such as too much heat.

B vitamin coenzyme. Catalyzes redox reactions

• NAD+ derived from niacin (vitamin B3). Can be reduced to NADH + H+

• FAD is derived from riboflavin (vitamin B2). Can be reduced into FADH2

• Briefly holds chemical energy

• Transfers chemical energy into an enzyme to power a chemical reaction (ATP turns into ADP)

• ADP gets recharged into ATP by the mitochondria in order to be used for a new chemical reaction

• Substrate-level phosphorylation

• Oxidative phosphorylation

Does not require oxygen. Chemical bonds are broken and energy from reactants is used to phosphorylate ADP into ATP. When done with glucose, this is glycolysis. Does not produce much ATP, mainly for quick energy such as a 1 minute sprint.

Requires oxygen. Energy from food creates a proton gradient (electron transport chain) that's used to attach phosphates to ADP. Produces much more ATP than substrate-level phosphorylation. For longer-term energy.

Substrate-level: around 2 ATP Oxidative: around 26 or 28 ATP

In the cytoplasm

Phosphorylated substrates. This normally occurs twice in glycolysis, and once in the Krebs cycle per molecule of glucose.

Energy from the oxidation of food is used to pump H+ across the mitochondrial membrane

True

Our blood sugar

Phosphorylated into glucose-6-phosphate. Prevents it from leaving the cell once it has already entered.

Facilitated diffusion

It keeps the intracellular glucose concentration low. ensuring continued glucose entry through diffusion

The catabolizing of glucose

1. Glycolysis and formation of acetyl CoA

2. Citric acid cycle (Krebs)

3. Electron transport chain (ETC) and oxidative phosphorylation

10

Anaerobic

Two pyruvic acid molecules

Loses 4 hydrogens. They bind to 2 molecules of NAD+, producing 2 NADH + 2H+

Net gain of 2 ATP. Glycolysis makes 4 ATP, but it costs 2 to start

NADH must donate its accepted hydrogen atoms to become NAD+ again. This allows it to pick up more H+ for the continuation of glycolysis

NADH returns its hydrogen to pyruvic acid which forms lactic acid. This allows NAD+ to continue to act as an electron acceptor

Lactic acid is oxidized back into pyruvic acid and enters aerobic pathways

In the mitochondrial matrix

Pyruvic acid from glucose breakdown and fatty acids from fat breakdown

It must be actively transported into the mitochondria

Transitional phase. This is where each pyruvic acid is converted to acetyl coenzyme A (acetyl CoA) if oxygen is available.

Another word for glycolysis

Loses a C as CO2 and two H atoms

Energy from FADH2 and NADH (move H+ from the mitochondrial matrix to the inter-membrane space)

ATP synthase phosphorylates ADP to ATP as the H+ diffuses

Process that forms glycogen from glucose. This happens when we have too much glucose. Muscles do this, and the liver does it often.

Glycogen synthase catalyzes the attachment of glucose into a chain of glycogen. This mainly occurs in the liver and skeletal muscle.

Breaks down glycogen

They split glycogen into glucose molecules

Glucose-6-phosphate

Glycogen is broken down in the liver into glucose, and it's transported in the blood to all tissues of the body

Process that forms glucose from non-glucose molecules, such as glycerol or amino acids. It maintains blood glucose when dietary sources and glucose reserves begin to deplete. It protects the body from hypoglycemia (low blood sugar) - especially the nervous system.

• Turning something new into glucose, even in the absence of carbohydrates

It enters the bloodstream to be used elsewhere in the body

It is used almost immediately by nearby muscle tissue

False. Cellular activity is important on the individual level as well as group level.

Their shape and form, as well as subcellular structures

Other cells

False. All cells have identical DNA, but different cells use this DNA differently.

Substances found outside of the cell

Interstitial fluid, blood plasma, cerebrospinal fluid

Jellylike substance of proteins and polysaccharides that help hold cells together. It's produced by cells themselves.

To control what enters and exits the cell, as well as what happens within. It's an active barrier that separates intracellular fluid and extracellular fluid.

A model that describes the cell membrane. It consists of a bilayer of fluid lipids (98%) within which are a variety of proteins

Two layers of phospholipids that make up the plasma membrane.

Horizontal movement, given that there is water in its environment to keep it in formation (with hydrophobic tails pointing inwards towards one another)

Go all the way through the plasma membrane. Involved with transport as channels or carriers.

Are attached to either the inside or the outside of the cell. Attach to integral proteins or to phospholipids, that may function as enzymes or in mechanical functions of the cell.

Fuzzy and sticky carbohydrate-rich are sticking out of a cell's surface that acts as a biological marker for identification among other cells. Some sugars are attached to lipids (glycolipids), and some to proteins (glycoproteins).

Selective permeability

On either side of the membrane, there are ions (electrolytes). Negatively charged ions are attracted to positive ones and vice versa. But, these ions cannot cross the membrane unless they are permitted to (unless a "door" opens).

75% phospholipids 20% cholesterol 5% glycolipids

(a) nonpolar (b) polar

A sugar coating on the outside of a cell/the cell membrane for identification

For charged substances. Forms a pore through the membrane which a specific ion can flow through. Most plasma membranes have specific channels for many common ions. Example: Although both are charged, the body recognizes K and Na differently and they have different channels. Integral.

For bigger substances. Transports a specific substance across the membrane by undergoing a change in shape. AKA transporters. Integral.

For chemical signals. Recognizes a specific ligand (chemical signal) and alters cell's function in some way. Example: Most hormones don't enter cells, they just bump into them, causing the receptor to change slightly and then it activates a message into the cell. Integral.

Catalyzes reactions inside or outside the cell (depends on which direction the active site faces). Example: Lactase can hydrolyze lactose so it can be easily transported into the cell. Example: Poly/disaccharides are too large, so enzymes can turn them into monosaccharides. Both integral and peripheral.

Bends into the shape that the cell needs. Anchors filaments inside and outside the plasma membrane, providing structural stability and shape for the cell. It could also help the cell move and link cells together. Both integral and peripheral.

Helps the immune system determine if the cells are self or non-self. Example: Blood type markers.

The binding of a chemical signal (ligand) to a membrane receptor. When the ligand binds, the receptor protein changes shape and becomes activated. This results in the initiation of a cellular response.

False. The same ligand can cause different responses in different cells depending on the chemical pathway that the receptor is part of (reactions are up to the receptor and not the ligand). Example: The same hormone affecting muscles vs. the GI tract vs. the brain differently.

A specific type of chemical signaling. Indirectly cause cellular changes by activating G proteins. G proteins can then affect ion channels and activate other enzymes. It essentially causes a chain reaction of signals. Example: About 30% of drugs use this method, which is why you only need a small amount of drug for a big impact. One cell messages ten, then those ten each message 100, then those hundred each message 1000, etc.

Cell Adhesion Molecules, part of the glycocalyx.

• Anchor cells to extracellular matrix/each other.

• Assist in movement of cells past one another.

• Attract immune cells to injured/infected areas.

• Stimulate synthesis/degradation of adhesive membrane junctions (ex. tight junctions).

• Transmit intracellular signals to direct cell migration, proliferation, and specialization.

Integral proteins that join adjacent cells to prevent molecules from passing through the extracellular space between cells

"Cell velcro" Scattered attachments along adjoining cells that reduce the chance of cells tearing apart when a tissue is stressed

Hollow cylinders of protein between cells that allow some small molecules to pass between adjacent cells, and are often used to conduct action potentials directly from cell to cell. Example: This is how the heartbeat is coordinated (it's one big contraction instead of many small ones)

A molecule will diffuse through the membrane if it's:

• Lipid-soluble

• Small enough to pass through a channel

• Assisted by a carrier protein

False. The growth, maturation, and division of a cell in its environment depends on itself, as well as the other cells that surround it. Example: Putting the foot bud of an chick embryo onto the extremity of its wing will cause it to have a mix of foot-like and wing-like characteristics.